Control apparatus



July 13, 1965 R. w. BROWN 3,194,296

CONTROL APPARATUS Filed July 26, 1965 3 Sheets-Sheet 1 J1y13,1'96'5R11/.BROWN CONTROL APPARATUS 3 Sheets-Sheet 2 Fi1ed July 2e, 1965 IOPDJOmm am July 13, 1965 R. w. BROWN CONTROL APPARATUS 3 Sheets-Sheet 3 FiledJuly 26, 1963 OPOS.

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QNPOJE m NQ N United States Patent O 3,194,296 CNTROL APPARATUS RichardW. Brown, Excelsior, Minn., assigner to Honeywell Ine., a corporation ofDelaware Filed July 26, 1963, Ser. No. 297,916 8 Claims. (Cl. 158-122)My invention is concerned with an improved control apparatus andparticularly a control apparatus which is adapted for use with-a fuelburner installat-ion to check and supervise a fuel valve of a fuelburner installation and to sound an alarm or the like if a leak should'occur at this valve.

As is well known, fuel burner installations may utilize variousarrangements of ignition means, pilot means, main burners and blower toprovide safe lightoff and operation of the main burner, under thecontrol of a controlling device responsive to the need for operation ofthe fuel burner. This control may be derived either as a result of apredetermined process requirement or as a result of the need for heat inan area to be maintained in a given temperature by operation of the fuelburner installation. Combustion safeguard means are provided tosupervise operation of the main burner, under the direct control of amain fuel valve which, when open, allows fuel to flow from a main fuelsupply pipe or conduit to the main burner where it is then ignited byignition means, for example a pilot burner. During the standby period ofoperation, when heat is not required from the fuel burner installation,the main valve is conditioned to be closed. Various failures may occurat this fuel valve, such as small particles of dirt lodging at the seatof the valve, to result in a fuel leak.

The apparatus of my invention provides improved control apparatus todetect such a fuel leak. I recognize that fuel leak detectors aregenerally old in the prior art. However, prior art fuel leak detectorsdo not function to provide the improved supervisory features which myinvention incorporates.

Specifically, the structure of my invention provides an .arrangementwhereby a fuel valve leak detecting apparatus includes a standing pilotwhich is associated with a thermocouple, a thermo-couple providing asafety pilot means to maintain flow of fuel to the standing pilot solong as llame is continuously detected at the standing pilot.Operatively associatedwith the standing pilot I provide a leak detectingpilot which is to `be ignited by the standing pilot in the event a leakoccurs. The leak detecting pilot is connected at the end of a fuel flowcircuit or pipe with a valve conditioned to be opened only when thethermocouple safety pilot detects llame at the standing pilot and onlywhen the main fuel valve of the burner installation is conditioned to beclosed. Thus, I allow the leak detecting pilot to be operative only iftwo conditions exist. The first condition is that the standing pilotmust be present to ignite the leak detecting pilot in theevent a leakoccurs. The second condition is that the main fuel valve must beconditioned to be closed.

As a further feature of my invention I provide flame detecting meanswhichis associated with the leak detecting pilot to detect flame only atthis leak detecting pilot. Furthermore, I provide an arrangement wherebyproper operation of my improved apparatus requires t'nat this llamedetecting means detect the presence of residual fuel which is downstreamof the main valve immediately subsequent to the closing of this mainvalve.

In other words, it is recognized that a residual amount of fuel willalways remain at a position downstream of the main valve immediatelyafter the valve is conditioned to be closed, and after it in fact doesclose. This residual fuel is supplied to the leak detecting pilot wherea molCe rnentary ame is produced. The structure of my apparatus requiresthat the llame detecting means associated with the leak detecting pilotmust detect this momentary llame to insure that the flame detectingmeans is in fact operative and is capable of detecting a llame.

Furthermore, I provide a timer which is energized only after the flamedetecting means detects this residual amount of fuel downstream of themain valve, the timer being conditioned to provide a timing period forburnoff of this residual fuel. As a result the apparatus of my inventionindicates a leaky valve, sounds an alarm, or closes a further safetyvalve which is upstream of the main valve, only when a sustained llameexists at the leak detecting pilot after this timing period.

With these general observations in mind, my invention will be apparentto those skilled in the art upon reference to the followingspecification, claims, and drawing, of which:

FIGURE l is a show-ing of a preferred embodiment of my invention shownin the de-energized condition,

FIGURE 2 is the same embodiment shown in the standby condition, and

FIGURE 3 is the same embodiment shown in the run condition.

Referring to FIGURE l, reference numeral 1t) designates a fuel supplyconduit which is connected to a source of fuel which is to be suppliedto a fuel burner installation, the components of which are not shown.

The flow of fuel to the fuel burner installation is under the control ofa main supply valve 11, having a winding 12 which, when energized, iseffective to open the valve and to allow fuel to flow to a conduit 13which is connected to the burners of the fuel burner installation.Energization of winding 12 of valve 11 is under the control of acontroller 14, shown as an open switch.

I have chosen not to show the components of the fuel burnerinstallation, and the manner in which controller 14 energizes thesecomponents since the exact manner and structure to accomplish this maytake many forms. Controller 14 may in fact be pressure responsive ortemperature responsive, and may be an automatic actuator to cycle thefuel burner installation automatically, to satisfy a condition to whichthe controller is responsive. It suffices to say that there are manyways in which controller 14 may operate a fuel burner installation toestablish flame at the burner installation. Furthermore, combustionsafeguard apparatus may be provided, and is usually provided, tosupervise theproper maintenance of flame at the fuel burnerinstallation.

My invention is concerned with detecting a fuel leak at valve 11 and itis intended that my invention be in addition to the normal combustionsafeguard devices provided at a fuel burner installation.

Reference numeral 15 designates a safety valve having a winding 16.Safety valve 15 is connected in fuel-flow series with valve 11 and, aswill be apparent, safety valve 15 is normally open and 1s closed onlyupon the detecting of a fuel leak, or upon a failure of a component ofthe fuel leak detecting system.

Reference numeral 1'7 designates a manual reset safety pilot Valvehaving a winding 18 which is connected to be energized from athermo-couple 19 associated with a standing pilot burner 20. As will beapparent, not only is valve 15 normally open, but valve 17 is alsonormally open to establish a standing pilot flame at pilot burner 20 toth-us maintain thermo-couple 19 heated to hold valve 17 open and tomaintain a switch 21 in a closed condition. Valve 17 is of the generaltype in which means are provided to manually open the valve. However,switch 21 is closed, and valve 17 is maintained open only ifthermocouple 19 is heated.

I have chosen first my apparatus in a de-energized conlWill be,energized Iat the appropriate time.

Referring-to electronic flame detect-ory 24, this amede tectorisofconventional design and includes a pair of elec- Y' Ydition, t-ofacilitate the explanationofthe initial sequence` Normally,Y however theof operation ofmy invention. apparatus is continuously energized vduringboth the standby (FIGURE 2) and the running (FIGURES) period ofoperation of an associated fuel burner installation.

" is transferred to a capacitor detector 24, is associated with leakdetecting pilot 22 and,

is responsive only tto. dame at leakdetecting pilot 22.:

Means may be provided to shield fiame'rod 23 from flame at standingpilot to insure that the ame rod does not detect a flame at the standingpilot. Y Y

Leak detecting pilot 22 is connected at the .end of ,a fuel conduit 124,having va blower 25 which, When'enerygized, is effective to cause themedium withinV conduit 124" Ito move in the 'direction of the'arrow,towardleak detecting pilotV 22. Also connected-in conduit 124 is avalveV i 26 having a winding V27 which is connected to be energized whenwinding 12 tof main fuelvalve 11 is de-energized. As will'be app-arent,blower25 andwinding V27 of valve 26 are energizedwhe'n the main fuelvalve 11 is .condi tioned to be closed and thus leak detecting pilot22sarnples themedium downstreanrof mainfuel valve 11 only during periodsin which valve11 is conditioned to be closed. Also, as is apparent,immediately after de-energization ofwinding 12 of valve 11, to conditionthisvalve to close,

a residual .amount of fuel remains in fuel conduit 13 downstream ofvalve Y11. This residual .fuel causes a momentary flame to beestablished at leak detecting pilot 22. This ame is detected bythe amedetecting means including flamerod 23 and electron-ic ame detector 24.

The' detection of residual fuel is necessary to establishv thevenergization of a timer 2S having a timer motor 29,21 clutch 30, Vandswitches A,YB, and C. The function of timer 28fis'v to timeV a giventime period lduring which burnof of resid-ual fuel takes place, and torender the fuel leak detecting apparatus elfective at the end of thistime period.

In the eventA of a fuelk leak, I provide safety cut-oft" means 31, inthe form of a bime-tal operated safety switch, Y having a bimetalactuator 32', a heater 33 therefor, a nor-- f mallyrclo-sed kswitch '34,Va normally -open switch '35, and

a manual reset button .':6. V Closed switch V34 of's'afety cutoff means31 isconnected in' series with Winding 16 of t-o be non-conductive. Thenonconduction -`ofi discharge device 57 lallowsconductionofhdisch'arg,'device SaitoV i energize a ameV relay 60, havinga winding61=gl`afnormally Y closed switch 62,.- and `a1norrnailyoperivswitchf, Such energiz-ation taking'place vupon the presence of iarrie;V

isnormally closed andclosing of thisswitchconnets the :primary windingsof transformers v67=and v68 to power line conductors. 64 uand 165,2itbeing-i assumed atthistime that there is no callV for operation ofanassociated fueliburner installationQand that controller, 14 is open.g;

The closing of switch66 completes an energizingfcirf..

cuit for valve 15 whichican ine-traced from power 'linefl conductor65.throughconductorsf90'and 105,;'v'alve windp-` Y ing 16, conductors163, 97 and 98,'switch '34, and conduc-y tors 99 and` 169 to powerlineconductor64.".5Fuel now `Y Y ows to 'the-upstream side ofvalvesrall' and ;17.

valve 15 and closes :this valve upon actuation of the safetycutofrlmeans. -The open switch of safety cutoffmeans 31 is connected inseries with an a1armf37 which, when;

open switches 42 and 43. A relay 44,having a winding 45 yand openswitches 46, 47, 48 and 49, is provided to be maintained energized onlyduring the standby condition of an associated fuel burner installation,and to be rstenerf f -giyzed during the detection of the burnotf ofresidual fuelimmediately alt the eind of a period ofV operation of themain fuel burner installation a-s a check for the operablityVV of amedetecting means'23-24. Relay 50, having a` winding 51,"normally closedswitches 52 and 53, and normallyopen V,switches 54 and`55`, is providedto sense a momentary power failure and nt-o also checkV electricalcontinuity of heater 33 to insure Lthat safety cutotl vmeans 31 isinfact operative. i Furthermore, vdeeenergization Vof winding 5i? iseffective, by means of switch 53,'toprovide a second.

energizingcircuit for alarm 37 to insure that this alarm tron dischargedevices 56 and 57 operating as a rectication type flame detector, Theoutput ofame rod'22z, when a ame is present at leak detecting pilot l22,is effective to charge a capacitor 58 to the polarity shown. 4This,charge Valve 17 yis then @opened manually; (Without closing `swit-ch21) andfstanding pilot'ZQ is ignited, to heat therrno f couple i19.vWhen :thermo-couple, 19 isheated suihciently, manual opening of;valver17 can Vthen '-bereleased and the Y.. valve remains open, ,withVswitch` vZ1" closed so 'long/.ass thermo-coupleV 19 continues to detectdame atstanding pilot Zilli n v f The energizat-ion oftransformer 67renders -ame d etec.- tor y 24 voperativthe cath-ode heaters ofthedi'scharge der. i vices56 and 57'notbeingshown. j p f Energizaticnfof transformer 6S .;..completesan initialY j energizing circuitfonwinding 45V of relaygld'by vai/erfV t a circuit whichcan be tracedfrom the. bottoml terminal" of the vsecondary winding Iof transforme-rv-tlilolgh con# iductior 69, sWitclrSZ V,of relay56,"conductors70,1'71andV 72, winding 45 o frelay -44jiconductor'73, switch41 of relay38,'and conductors 74 and 4,75 tothe upper terminal of thissecondary'winding'. v,Er'1e1f,gizf,atio'n 4of thewinding 45 of relay44'is effect-iveto actuateitheswitches Vof thisy relay. The closingofswitch-.tdcompletesfaholdingc-ir- Y cuit to energize the. windingof'rela'y 44, this'fcircuit being: traced .from the llowerterrninalofthefsecondary Ywinding i oftr-ansformer; through conductors-69,l'l6`and :77, switch a' 46, conductor 72, winding45, conductor[73 switch41;, and conductors 74Y and .75, Vto. theV upper Vterminal tof Vthissecondarywinding; 5.

ing.. Y

Theclosin'g obswitch 48;.completesa circuit-which l shunts heaterfv?,`jduring the i standby condition ,off the g Y `fuel burnerinstallation-,hut fonlyso longas ame de- Vtector 24 does not detect thepresence .of flame'at leak detecting pilot `2.2i` VThis shuntV circuitcanfbe traced from the upper terminal vof heater 'throughconductors y80,75 gandVSl, switchf48conductors 82 and 83swith v 62-,and conductors84,5185 and 79'to Vthelowerv terminal -o'fheater33;;V Y

Energization vof "blowerY 25.; is rj'achieve'd" by g means of a lcircuit whichcan -be` vtraced from-power,lineconductor 'Y 65'throughconductors l90 and; 91;;s'W/itch4t), fconductors Y conductors96,197 ,and 98;switchv4',Sandconductors 99 i Y and 100 to powerline,co'nductorr64..YV Y

An energizing circuitV fonwinding 27` 'of valve Y26 :can be traced fromthe above'mentionedtonductor 94 through Stobias discharge device57 YTheA closing `of switch f 47v completes an"ene`rgizing VcirY cuit forwinding 51 .of reim/...570, whichjcanbe traced fromthe lower,terminalfof fthe, second-ary winding of-.`V transformer 68 throughconductors 69 and 76, switch `47,'

conductor 78, winding 51?,.conductorj79,fheater 33, fand a i conductortol theupper terminal fthissecondary wind- 99 and 100 to power lineconductor 64. Thus, valve 26 is conditioned to open and blower 25 isenergized.

With both relays 44 and 50 energized,l an energizing circuit iscompleted for timer 28. This energizing circuit can be traced from powerline conductor 65 through conductors 90 and 91, switch 40, conductors92, 93 and 104, clutch 30 and motor 29, conductor 105, switch 49, con'-ductor 106, switch 55, conductors 107, 97 and 98, switch 34, andconductors 99 and 100 to power line conductor 64.

The energization of motor 29 and clutch 30 is effective to causerotation of the motor, and as indicated, switch B closes at secondsafter energization of motor 29 and clutch 30. Switches B and C, inseries, form a circuit which shunts the closed switch 62 of flame relay60 to allow frame relay 60 to respond to the residual fuel downstream ofvalve 11 immediately after the closing of this valve without causing theenergization of heater 33.

At the one minute interval, switches A and C open. The opening of switchC again places flame relay 60 in a condition to supervise energizationof heater 33 of cutoff device 31 suchthat this heater is energized asflame is detected asa result of an actual fuel leak. The opening ofswitch A de-energizes motor 29. The switches A, B and C are maintainedin their actuated positions by virtue of continued energization ofclutch 30. Timer 28 is a spring return timer and subsequentde-energization of clutch 30 causes switches A, B and C to return to theposition shown in FIGURE 1,

The apparatus is now in a standby condition as shown in FIGURE 2 whereinvalves 15 and 17 are open, valve 11 is closed, valve 26 is open, blower25 is energized, timer 28 is in its actuated position with switch Aopen, switch B closed and switch C open, relay r30 is de-ener gized, andrelays 44 and 50 are energized.

The medium downstream of main valve 11 is drawn through open valve 26,by means of blower 25 and is presented to leak detecting pilot 22. Ifthis medium, or atmosphere, contains fuel, this fuel is ignited bystanding pilot and is detected as a fuel leak by flame detecting meanswhich includes flame rod 23 and electronic fiame detector 24.

I will now describe the sequence of operation which takes place upon aneed for operation of the associated fuel burner unit, as is evidencedby the closing of controller 14. The closing of this controller effectsenergization of winding`39 of relay 38, to actuate its associatedswitches. The opening of switch 40 is effective to` de-energize theprimary winding of transformer 67 associated with flame detector 24,this primary winding being connected to power line conductor 65 throughswitch 40. The opening of switch 40 is also effective to de-energizewinding 27 of valve 26, blower 25, and timer clutch 30. Switch 42 shortsheater 33 of safety cutoff `device 31 dur ing the run cycle of theassociated'fuel burner installation. The opening of switch 41 iseffective to de-energize winding 45 of relay 44. Y The closing -ofswitch 43 is effective to complete a energizing circuit for winding 12of Valve 11. This ener gizing circuit can be traced froml power lineconductor 65 through conductors 90, 105 and 106 to winding 12, conductor207, switch 43, and conductors 108 and 209 to power line conductor 64.Thus, valve 11 is conditioned to open and fuel flows to the associatedfuel burner unit. The de-energization lof relay 44, as a result of theopening of switch 41, is effective to cause its switches 46 and 47 toopen. The opening of switch 46 opens the above traced holding circuitfor winding 45 of relay 44. The openingy of switch 47 opens the circuitwhich previously shunted the closed switch 54 -of relay 50 and thusrelay 50 is maintained energized by way of a circuit which includes onlyits closed switch 54.

. In the event of apower failure at this time, it is necessary that thestarting cycle be repeated to energize relay 50.

The apparatus is now in the run condition as shown in FIGURE 3 wherevalves 15 and 18 are open, valve 11 is open to allow fuel to fow to thefuel burner installation, valve 26 is closed, blower 25 is deenergized,flame detector 24 is inoperative, timer 2S has reset so that switches A.and C are closed and switch B is open, relays 38 and 50 are energized,and relay 44 is de-energized. This condition remains until the end ofthe period of need for operation of the associated fuel burner unit.

At the end of a call for operation of the associated fuel burner unit,as evidenced by the opening yof controller 14, relay 38 is againde-energized. The de-energization of this relay connects the primarywinding of transformer 67 to power line conductors 64 and 65 to renderthe electronic flame detector 24 operative. Furthermore, main valve 11is closed and the fuel leak detecting apparatus, including valve 26 andblower 25, is actuated. At this time there is residual fuel in fuelconduit 13 downstream of main valve 11. This residual fuel produces aflame at leak detecting pilot 22. This flame is detected by means 23-24and as a result flame relay is energized.

The energization of ame relay 60 causes switch 63 t-o close. The closingof this switch is effective to complete an energizing circuit for relay44. This energizing circuit can be traced from the lower terminal of thesecondary winding of transformer 68 through conductors 69, 109 and 110,switch 63, conductors 111, 71 and 72, winding 45, conductor 73, switch41, and conductors 74 and 75 to the upper terminal of this secondarywinding. Thus, energization of relay 44 is evidence of the operabilityof means 23-24 to detect the presence of flame.

As .soon as relay 44 is energized, the above t-raced energizing circuitfor motor -29 and clutch 30 -of timer 2S is completed to institute afuel burnoff period, but to institute this period only if fiamedetecting mean-s 23-24 has proven to be operative.

After a `short interval of l5 seconds, yswitch B of the timer closes toshunt heater 33 of safety cutoff means 31. In the event that flamedetector 24 had failed and did not detect the presence of flame which isknown to exist las a result of the residual fuel downstream of mainvalve 11, heater 33 of safety cutoff means 31 would have remainedenergized and, after a time period of energization, safety cutoff mean-s31 is actuated to open switch 34 and to close switch 35. As has beenmentioned, the opening of switch 34 is effective to close valve y15 asan additional safety feature and to energize alarm 37.

Normally however flame detector 24 is operative Iand as a result timer23 lis energized. However my apparatus first checks the opera'bility ofthe flame detector and institutes the residual fuel burnoff timing onlyafter the fiame detector operability has been proven.

rifimer 28 allows a one minute period for burnotf of the residual fuelwhich is known to exist downstream of valve 11. After this one minuteinterval, switch C is opened and heater 33 of safety cutoff means 31 isagain placed under the supervision of flame relay 60. In the event thatValve 11 has failed to close, and that a leak thus exists -at the valvesleak detecting pilot 22 continues to .sustain a flame and flame relay 60remains energized# So long as this relay remains energized, heater 33 ofsafety cutoff means 31 is also energized and after an additional timeperiod (the timing period of means 31) valve 15 is closed and alarm 37is energized.

Furthermore, if at any time during the standby period of the associatedfuel burner installation (the period of which controller 14 is open) afuel leak develops at valve 11, flame relay 60 is energized and heater-33 is then energized. After the timing period of safety cutoff means31, valve 15 will close and alarm 37 will be energized.

From the above description it can be seen that I have provided animproved control apparatus of a type to detect a leak vat a fuel valve,and that my apparatus is constructed and arranged to utilize a standingpilot such that residual'fuel which islknown to exist,gis Ainstitutedonly afterrthe residual fuel has been detected by Van associated iiamedetector. Thus, I provide aniarrangernent Wherebythe variouscomponents'arey checked, one Vagainst the lother, to insure that variouspossible Vcomponent'failures do not result in unsafe operation andreliancejon the operabilityY of'the 4control apparatus, when suchoperability 10 burnensysterncomprising:V V

Other modifications of my invention will be apparent to those skilled inthe art as it is thus intended that;l the? scope of my invention belimited only` by thescope of does not in fact exist. .Y

the appended claims.

claim as my invention: 1. Fuel leak detecting apparatus comprising: afuel burner unit,

a fuel conduit connected between the fuelburner Vunit` Vand asource offuel, t Y

` a main vfuel valve connected in the fuel conduit and adapted to admitfuelto the 4fuel burner unit onlyvv during periods of aneed foroperation of the ,fuel

burner unit, Y Y a controller operable to determine the periods of aneed Y foroperation of Vthe' fuel Vburner unit, V

Va iirst pilot burner having-firstV flame sensing meansy cooperatingtherewith to sense Vthe presence or absence of flame, Y Y Ya safetypilot valve connected between the fuel conduit and said fir-st pilotburner, controlled 'by said first;

cooperating therewith to sense the presence Vor ab" sence of llame, saidsecond pilot burner being'adapted tovbe mounted in cooperating relationto said iirst second amefsensing meansfrespofn'sive,toflameatsaid, Y i

pilot burner so that fuel Vat said second pilot burner is ignited byii-ame at said first pilot burner,

Vmeans including a further valve'a-dapted to be connected" Yto thefuellconduit at favposition downstream from the mainpvalve and to 'beconnected to said'se-cond pilot burnerV to admit'fuel at said positiondownstream i to said second pilot burner, K meansV adapted to becontrolled 'by the controller and by said first flame sensing means tocause said further valve to open only when flame is sensed at said iirstpilot burner duringl a period when there is no need for operation ofthefuel burner unit,

and means controlled by'j said second flame sensingV means toprevent'fuel iiow tothe fuel burner unit in 'the event of a fuel leak atthe main valve as evidenced o Va fuel valve connected in ysaid fuelsupply conduittoi*A control'the flow of fuel therethrough, v

-liame sensing means responsive to a tiame atvsa-id` pilot5 burner, Y

controllable fuel flow means adapted to be connected to g the fuelsupply conduit at -a position downstreamof 'I thefuel valvetoselectively sample for fuelwithin the "fuel supply conduitrat vsaidposition downstream,

i a second pilot burner operatively associated with saidcontrollablefuel flow means and with said continu.-

i ously burner pilot burner so that fuel supplied to said second pilotburner by said fuel .flow means is ignited by said continuously burningpilot burner,

means includingsaidflame sensing means adapted tol control -saidrfuelflow means to connect said second pilot burner jin fuel flow relationytoisaid position downstream of the fuel valve only whenthe fuel'.

fuelvalve; the apparatus comprising:`

valve isic ortd-itionedLtoibo closed fat a time V:when a` Y fiar/nev issensed Y at said continuously burning pilot: burner,

and means including second flamesensing meansjr'espony sive only to aVflame Iat said 'secondf pilot burner for preventing fuel flow throughsaid fuel-sut'ply'conduit,Vv

' in the event ofarne being presentatY saidsecond pilot 3.;Fue lY'lealcdetecting apparatus ffor'usejywith Ya fueljf a fuel supply conduitconnected between said fuelV burn-f p erand arsoureof fuel 'y f' t amain valve in saidi fuel supply conduit to control-the', lfuel'tosaidfuelburner; N i

a continuously-,burning:pilot: Vburner. andrst flame sensingI` meansresponsive; to :the presence Y of name -thereat,

a second pilot burner associated` with` said continuously.

burning pilot burnelrso, that saidpontinilously burni ing* pilotburnerconstitutesfigniting means. 'fonsaid f secondpilotburner, L p, Y i gsampling; means inclt1ding-a -normally closedrvalve and` a fuelconduit"adapted:tobejconnected tosaid sec-f ond .pilot burner and tothefuelsupply conduit atl a Aposition intermediate the Vfueljlburner and;the;A mainfuelvalve,V means including: said first liame sensing meansto ene t giletsaidnormallyclosed, valvelonlyfwhen' the. main i fuelyalve-is conditioned tobe closed atiaftirnewhenf` l Y va ame is sensedat-'saidvcontinuously tburningipilot; `burner,y l

secondpilotburner, Y v checking vmeans 'controlled by Vsaidsecond flamesensing means and operative upon 'themornentary'estab-f 1ishmentof-ameat said second gpilot` burner due-"to lresidual fuel; at theVposition"intermediate theV fuelv burner and theffmain yfuellvalve@as-ffuelan-orrnally existsy immediately;` after closing =of thezmain' fuel f valve,VV Y and safety means Ycontrolled by'saidsecondYflame sens- VVing means andoperative upon :the presence of; apro-tY Ylonged liameatsaid second Vpilot afterthenclosingfoftf V1 Y the :mainvalve to` prevent fuel owf1hr91igh5ai@ i 4x Fuel leakdetecting:apparatus Vfor a ifuely burner. system, operativeto detect ajfu'elgleaklatr a main d 1 afuel burner system, Y 'Y e s Y a fuel supplyconduitjccmn'ectedbetweensaid:fuellburnnY er system anda source'offuel,L i

a main fuel valve having anoperator, saidrmain fuelz valveconnected insaid fuel supply conduitto conl trol the fueliiow therethrough l v y r YAa continuously ',burning 'pilot burner fanddirst llameV sensing means.responsive to the; presence of llameV Vthereat Vto',maintainL-fueliiiow..tosaid continuously burning pilotburner,v l i asecond pilot uburnerl associated with said continuouslyVV buring pilotburner, said v continuouslyA buring pilot :1

burner constituting -ignition meansjgfor E said second zg tVpilotburn'er, 1

sampling means Vincluding aV normallyfclosedY valve and" Y Y' asamplingconduitiadapted V"to be connected to saidsecond pilot burner andto the fu'elj'supply` conduit ataposition Whichisintermediate'fthefuel-.burner system andthe mainfu'elyalvef* 'v p ,Y l means includingsaid ,rfstV Harrie sensing f 'rneansLV Var -fV ranged to open saidnormally closed ,valyeonlywhen the main fuellvalve operatorjisconditioned to' Vclos'e} V the main fuel valve at a time when a me'issensed at said continuously burning pilot burner, i

vsecond flame sensing means responsive to flame at said second pilotburner, timing means,

checking means controlled bysaid second flame sensing means andoperative upon the establishment of ame `at said second pilot burner dueto the presence of residual fuel which exists at the positionintermediate the fuel burner system `and the main fuel valve immediatelyafter the closing of the main fuel valve,

means including said checking means to energize said timing means tobegin a timing interval for burning off of the residual fuel uponoperation of said checking means,

and safety means controlled by said second flame sensing means and bysaid timing means and operative upon the presence of liame at saidsecond pilot burn er after'the expiration of said timing interval toprevent fuel flow to said fuel burner system.

S. In combination: t

a fuel burner unit having a main valve to control the flow of fuel to amain burner,

a controller operative to selectively control said main valve to be openor to be closed,

a continuously burning first pilot burner having first flame detectingmeans associated therewith to maintain fuel flow to said first pilotburner so long as flame is detected thereat,

a second pilot burner, arranged to be ignited by said first pilot`burner, having second flame detecting means associated therewith to beresponsive only`to a llame at said second pilot burner,

a fuel flow conduit connecting said second pilot burner to thedownstream side of said main valve, said fuel ow conduit including meanscontrolled by said controller and by said first flame detecting means toallow said second pilot burner -to sample for fuel at the downstreamside of said main valve only when said main valve is controlled to beclosed at a time when flame is detected at said rst pilot burner,

time delayed safety cutout means having an actuator and switch means tobe actuated after a time period of energization of said actuator,

means to render said safety cutout kmeans actuator inoperative when saidmain valve is controlled to be open,

a relay having a winding and switch means controlled thereby, checkingmeans to check the operating of said second llame detecting means andincluding said relay winding to initially energize said relay windingwhen said main valve is initially controlled to be closed and a flamedetected at second pilot burner, means including said relay switch meansto subsequently maintain said relay Winding energized so long as saidmain Valve is controlled to be closed,

a timer, including switch means, to time for a given interval theburnoif of residual fuel at the downstream side of said main valvesubsequent to said main valve being controlled to be closed, meansincluding said relay switch means to energize said timer uponenergization of said relay winding,

means including said timer switch means and said relay switch means torender said safety cutout means actuator inoperative during said giveninterval,

and means including said second flame detecting means to render saidsafety cutout means actuator operative if llame is detected at saidsecond pilot burner subsequent to said given time interval.

6. Control apparatus for use with a fuel burner unit comprising:

a main burner,

a main valve adapted to control the How of fuel to said main burner,

a controller operative to selectively control said main valve to be openor closed,

a continuously burnin-g first .pilot burner having first Itia-medetecting means .associated therewith to maintain fuel flow to saidiirst pilot burner so llong as flame is detected thereat,

-a second pilot burner, arranged to be ignited by said iirst pilotburner, and having second flame detecting means associated therewith tobe responsive only to a flame at said second pilot burner,

a fuel liow conduit adapted to connect said second pilot burner to thedownstream side of the main valve, said fuel flow conduit includingmeans adapted to be contnolfled bythe controller and by said first flamedetecting means lto sample for fuel at the downstream side of the mainvalve only when the main valve is controlled tobe closed at a time :whename is detected at said iirst pilot burner,

time delayed safety cutout means having an actuator and switch means tobe actuated after a time period of energization of said actuator,

Y a relay having a wind-ing and switch means controlled thereby,checking means to check the operation of said second llame detectingmeans and including said relay winding to initially energize sa-id relaywinding when the main valve is initially controlled to be closed andt-he residual fuel downstream of the main valve causes a liame to bedetected at said second pilot burnerrmeans including said relay switchmeans to subsequently maintain said relay wind-ing energized, v

a timer, including switch means adapted to time for a given timeinterval Ithe burnolf of the residualr fuel at the downstream side ofthe main valve subsequent to the main valve being controlled to beclosed, means includ-ing said relay switch means to energize said timerupon energization of said relay Winding,

means including said timer switch means and said relay switch means torender said safety cutout means actuator inoperative during said ,giventime interval,

and mea-ns including said second flame detecting means to render saidsafety cutout means actuator operative if flame is detected at saidsecond pilot burner subsequent .to said given time interval.

fl. Control apparatus for use with a fuel burner unit comprising:

a main burner,

sa main valve adapted to control the flow of fuel to 'said m-ain burner,

a controller operative to selectively control said main valve to be openor closed,

, ya continuously burning tirs-t pilot burner having rst iame detectingmeans associated therewith,

a second pilot burner, arranged to be ignited by said iirst pilotburner, having second flame detecting means associated therewith andadapted to be responsive only t-o a ame at said second pilot burner,

a fuel flow conduit adapted to connect said second pilot burner Vto theldown-stream side of the main valve, said vfuel ow conduit includingmeans adapted to be controlled by said controller and by said tirstflame detecting means to facilitate sampling for fuel at the downstreamside of the main valve only when the main valve is controlled to beclosed at a time when ame is detected at said first pilot burner,

time delayed safety cutout means having an actuator and switch means tobe actuated after a time period of energization of said actuator,

means to render said safety cutout means actuator inoperative when saidmain valve is controlled to be open,

a first relay having a winding and switch means controlled thereby,checking means to check the operation of said second flame detectingmeans and including said first relay winding to initially energize saidfirst relay Winding when the main valve "is inirtially controlled to beclosed and a ame is *detectedA at lsaidsecond pilotburner as Va resultof residual Y fuel, means including said rst relay'switch Ameans tomaintain said rst relaywindin-g energized when'a diamo .is thusdetected,

a second relay having :a winding and switchrtmeans controlled thereby,meansV including said second re- .lay winding andlcontnolled by said rstrelayzswitch"A means to initially energize said 'secondrelaywindfingiupon energization o'f said firstv relaywinding,

.means including said second relay switch means to maintain said vsecondrelay wind-ing energized,V

mea-ns including said first relay-winding and controlled by said secondrelay switch l*means* to energize said iirs't Vrelay Winding Vwhen the-m'ain yvalvev iscontrolled tobe closed andfsaid second relay Winding isdeencrgizedL a timersv including'switch means, adapted'to time for` a-given time interval theburnoliof residual fuel at the downstream sideo'f-` the main kvalve subsequent to the main` valve being controlled toIbe closed, means Y including said irsftgandjsecond* relay switch meansto energize said timer lupon energizjation ;of said r'st and-secondrel-aywindings; .i

means including said timer'switch means and said-first relayswitchvmeans toirender said safety cutout means `actuator inoperativevduring said given time- Y interval, Y t ,Y g

and means includinggsaid second flame detecting means Ato render saidsafety cutout means vactuatorv operative when llame is detected Vatsaidzsecond pilotVV burner g subsequent to said given time interval.

58. Contr-o1 apparatus for use with a fuel vburner unitA toV detect afuel leak ata given portion ofthe fuel burner unit, Y comprising: t

a fuel burner unit',

l controller means operzaljlyY connectedto -said lfuelf burner unit, I

y a continuously burning" pilot burnerfand a rstarnef Y Ydetector:responsive yto name :thereatt 'Y Y t a second'pilot burnerfarnanged tobelignitednby'sai continuously burningqpil'otburner and'h'aving :acor'v' ytroll-able fuel ow conduitadaptedrto be connected toa -givenportion o'f the fuelfbriutnerrunitgf,41 Y i means controlled byfsaidrstfilamead-etector"andgsaid tiona-llybeing admitted thereto; i Y

second flame detectingxmeans.responsive toilamewat Y Ysaid'secondvpilot'iau'rnerg residual fuelis normally-burned ofi." 4',Referensciie'd-byfne Examiner y `UNITED siATEs PArElsIIsY ,z5-32214;`1li/5o FREDERICK 1L.' MATTEsoNJn, VPrimm-y' Examinewf MEYER v PERLIN; fJAMESV WESTHAVER;

controller `means Vtofsazmp-l'eior fuelfat `the given por-f tion of the`fuelbiirnei unit wfhenifuel `is not V-intenv Y

1. FUEL LEAK DETECTING APPARATUS COMPRISING: A FUEL BURNER UNIT, A FUELCONDUIT CONNECTED BETWEEN THE FUEL BURNER UNIT AND A SOURCE OF FUEL, AMAIN FUEL VALVE CONNECTE IN THE FUEL CONDUIT AND ADAPTED TO ADMIT FUELTO THE FUEL BURNER UNIT ONLY DURING PERIODS OF A NEED FOR OPERATION OFTHE FUEL BURNER UNIT, A CONTROLLER OPERABLE TO DETERMINE THE PERIODS OFA NEED FOR OPERATION OF THE FUEL BURNER UNIT, A FIRST PILOT BURNERHAVING FIRST FLAM E SENSING MEANS COOPERATING THEREWITH TO SENSE THEPRESENCE OR ABSENCE OF FLAME, A SAFETY PILOT VALVE CONNECTED BETWEEN THEFUEL CONDUIT AND SAID FIRST PILOT BURNER, CONTROLLED BY SAID FIRST FLAMESENSING MEANS TO ALLOW FUEL TO FLOW TO SAID FIRST PILOT BURNER SO LONGAS FLANE IS SENSED THEREAT, A SECOND PILOT BURNER HAVING SECONG SENSINGMEANS COOPERATING THEREWITH TO SENSE THE PRESENCE OR ABSENCE OF FLAME,SAID SECOND PILOT BURNER BEING ADAPTED TO BE MOUNTED IN COOPERATIONRELATION TO SAID FIRST PILOT BURNER SO THAT FUEL AT SAID SECOND PILOTBURNER IS IGNITED BY FLAME AT SAID FIRST PILOT BURNER, MEANS INCLUDING AFURTHER VALVE ADAPTED TO BE CONNECTED TO THE FUEL CONDUIT AT A POSITIONDOWNSTREAM FROM THE MAIN VALVE AND TO BE CONNECTED TO SAID SECOND PILOTBURNER TO ADMIT FUEL AT SAID POSITION DOWNSTREAM TO SAID SECOND PILOTBURNER, MEANS ADAPTED TO BE CONTROLED BY THE CONTROLLER AND BY SAIDFIRST FLAME SENSING MEANS TO CAUSE SAID FURTHER VALVE TO OPEN ONLY WHENFLAME IS SENSED AT SAID FIRST PILOT BURNER DURING A PERIOD WHEN THERE ISNO NEED FOR OPERATION OF THE FUEL BURNER UNIT, AND MEANS CONTROLLED BYSAID SECOND FLAME SENSING MEANS TO PREVENT FUEL FLOW TO THE FUEL BURNERUNIT IN THE EVENT OF A FUEL LEAK AT THE MAIN VALVE AS EVIDENCED BY THEPRESENCE OF FLAME AT SAID SECOND PILOT BURNER.